Method of controlling the properties of metals and metal alloys by irradiation with vibrations



g- 1958 L. J. ETTENREICH METHOD OF CONTROLLING THE PROPERTIES OF METALSAND METAL ALLOYS BY IRRADIATION WITH VIBRATIONS 3 Sheets-Sheet 1 FiledSept. 17, 1953 fie 2 J, ErrEAm/m IN VEN TOR.

Aug. 26, 1958 L. J. ETTENREICH 2,848,775

METHOD OF CONTROLLING THE PROPERTIES OF METALS AND METAL ALLOYS BYIRRADIATION WITH VIBRATIONS Filed Sept. 17, 1953 s Sheets-Sheet 2 14.1 ML /si [wing 1% 4 2/ IHIIIIIIIIII IN VEN TOR.

Aug. 26, 1958 L. J. ETTENREICH 2,848,775

METHOD OF CONTROLLING THE PROPERTIES OF METALS AND METAL ALLOYS BYIRRADIATION WITH VIBRATIONS 3 Sheets-Sheet 3 Filed Sept. 17, 1953 mm Km8 R LR QR 8w E aw H N .m n n L m 5 J m 2 N x 3 s .Qw NN N INVENTOR.

Patented Aug. 26, 1%58 Ludwig Josef Ettenreich, Woifurt, Von-Ari erg,Austin, assigner to Etnia S. A Panama, Panama, 2. corpora tion of PanamaApplication Eiepternher 17, 1953, Serial No. 380,812

16 Claims. (Cl. El -2490) This invention relates to a method ofcontrolling the orders of magnitude of the properties of metals andmetal alloys, for example steel, by subjecting them, in their solid ormolten state, at temperatures corresponding to, or above the phaseconversion state to the influence of vibrations of appropriatefrequencies from an external source.

An object of the instant invention is so to control the atomic andcrystallographic structure of the treated material throughout the entirebody of the material in accordance with predetermined requirements ofhardness, tensile strength and grain size, of which the material asjudged by its qualitative and quantitative composition is capable.

A further object of the invention as applied to the treatment of steelis to produce a predetermined desired solution of its carbon constituentin the iron thereof, together with the attendant physical properties inthe steel, without withdrawing energy suddenly from the steel.

Still a further object of the invention as applied to the treatment ofsteel is to supply energy electrically, acoustically or otherwise, tothe steel at temperatures at or above a determinable temperature toproduce predetermined and desired physical property values in the steelwhich are retained by the steel at normal temperatures.

Still a further object of the invention, as applied to the treatment ofsteel, is to produce predetermined improved physical properties inordinary carbon steels which improved properties are of orders ofmagnitude of the physical properties of alloy steels.

Still a further object of the method is to permit of the casting ofmetal products in their final dimensions and treating them in the castand heated condition in such manner as to improve their physicalproperties without interrupting or accelerating the cooling thereof, andto retain the improvement so obtained when the cast metal products havesolidified and cooled.

Still a further object of the invention, as applied to the treatment oflight-alloy steels, as well as mediumalloy steels, is to improve thephysical properties thereof to substantially the same order of magnitudeas those presently of the more heavily alloyed steels.

Still a further object of the invention, and particularly as applied tothe hardening of steel, is to eliminate present requirements in respectof the small time intervals within which the cooling or quenching mustbe efiected to produce a required degree of hardness, and yet to obtainany required degre of hardness Wholly independent of the cooling time.

Still a further object of the invention is to permit hardening carbonsteels, within their hardenable range; to the very core thereof to suchvalues as are presently associated with alloy steels.

Prior methods of controlling the values of the properties of materials,particularly metals and metal alloys, by influencing their atomic andcrystallographic structur.

have generally taken the form of heating followed by quenching, that is,have involved the extraction of energy from the material being treated.More recently, methods have been suggested of so controlling suchstructures in materials, metals and metal alloys, by subjecting them inheated condition to supersonic vibrations. Probably due to the highorder of damping of the frequencies involved, only surface effects havebeen obtained rather than the desired uniform effect throughout thewhole body of the material being treated. Even to produce such surfaceeffects as the supersonic methods are capable of, considerable time wasrequired, although as compared to methods involving quenching, thesupersonic methods are based on the principle of energy addition to thematerial being treated. It appeared to me that the principle of energyaddition to control the physical properties was basically correct, butthat in these supersonic methods the source of the external energy addedto the material was rather the most unfavorable one that could be usedin view of the high damping rate of supersonic frequency generators.Furthermore it appeared to me that the use of supersonic frequencies notrelated in any fixed way to the material under treatment probablycontributed to the results obtained, namely, the inadequate surfaceeffects and the failure to produce effects uniform throughout the bodytreated. By subjecting bodies to the influence of supersonicfrequencies, a loosening of the atomic structure as well as a decreasein the grain size was produced. Based upon theoretical considerations,since supersonic methods of irradiation produced only surface effectsand since low frequencies in the audio range could readily be sustainedwithout any damping, irradiation by the use of low frequencies mightwell penetrate throughout the body being treated. However, with onlythat knowledge and in the absence of the phe nomenon first observed andrecognized by myself, the use of low frequencies would appearimpractical as involving too much time.

The instant invention overcomes the difficulties of the supersonicmethods and is based on the following phenomenon first discovered andrecognised by myself as to the characteristic nature thereof. Any bodyof matter, and particularly of metals or metal alloys, composed of atleast two constituents, or composed of a major and at least one minoringredient-whether such minor ingredient is found with the majoringredient in the latters natural state or is added thereto in theprocessing thereofin addition to its natural or resonant sinusoidalvibration of a given frequency, determined in the main by the majoringredient of the particular body, has a second characteristic vibrationof which the frequency is dependent on the order of magnitude of thephysical properties of the body produced by the minor ingredient,respectively ingredients. Only in the case of bodies of a singleconstituent which is substantially chemically pure has such a secondcharacteristic vibration not been observable. This second characteristicvibration differs slightly in frequency from the frequency of thenatural or resonant vibration, being always somewhat higher as observedand measured, and is also of sinusoidal wave shape. Since the twofrequencies differ but slightly from each other a resultant, relativelylow frequency beat vibration is produced. The natural or resonantfrequencies of bodies are obviously considerably below the supersonicfrequencies used in the prior methods attempting to influence andcontrol the physical properties of bodies, and in practical cases areseldom in excess of some 3,000 cycles per second extending downwardly toa few cycles per second or less.

In the following portions of the specification and in the claims theterm natural frequency is always used to define the lower of the twofrequencies at which a body of material of at least two componentsvibrates.

when left to itself to vibrate freely after having been set in vibrationby an application of an external force and suchexternal force hasterminated.

I was the first to recognize that the beat vibrations which occur in anelastically anisotropic medium or body are relate'd to the values of thephysical properties of such body and that:

a. The frequency of the beat vibration is a function of the physicalproperties of the body, such as hardness, tensile strength, and grainsize, varying in relation to such values, and increases with increasesin the values of the hardness, tensile strength, and fineness of grainstructure;

b. By impressing beat vibrations of a given frequency upon such a body,and thus also the energy of such beat vibrations, the value of thephysical properties of such body may be varied since each value of thephysical properties of such body corresponds to a beat vibration of adefinite frequency characteristic of the particular value; and

c. To control the physical'property values of the body by impressing abeat vibration of a given frequency upon such body, one of the twosinusoidal oscillations producing the beat vibration must have afrequency equal to the natural frequency of the body.

The above can be explained in greater detail as follows: By the methodof my invention changes in the values of the physical properties of suchbodies, particularly in the case of steel bodies, are caused byproducing n ferent velocity of transmission of the wave in differentdirections, are divided into two components. In that the two'componentsare coherent, i. e., have a common point of origin, and, as shown byobservations and experience, are of but slightly different frequencies,they interfere with each other in the form of a beat vibration. In thephysicalsense a beat vibration is the resultant of two sinusoidaloscillations, the frequency of the beat vibration being the differencein the frequencies of the oscillations producing it and'of which theamplitude is a periodic function of time. A heat vibration of which onecomponent sinusoidal oscillation is the natural frequency of the body ishence designatable as a natural beat vibration of the body.

This natural beat vibration, and only this natural beat vibration, ischaracteristic of the particular value of the physical property of abody of a given material. Only this .natural beat vibration, that is,the energy inherent in such natural beat vibration, can be used to varythe order of magnitude of the values of the physical properties of thebody to a predetermined and desired value. Each value of a physicalproperty, such as hardness, ductility, tensile strentgh and grain sizefor example, corresponds to and has a definite energy content. If then,the value of such physical property is to be altered, there musttherefore be applied to the body at least such a quantity of energywhich quantitatively totals to that of the desired value of the physicalproperty. l

My tests haveuniformly shown that for a given configuration and a givenmaterial, 'the natural frequency remains unchanged but that thefrequency of the natural beattvibration increases with the hardness of:the body.

Taking bodies of identical material throughout the bodies and of thesame geometrical configuration and dimensio'ns, I have tested theirhardness in the untreated condition and in conditions after treatment tovarious degrees of hardness. Irrespective of the mode of treatment bywhich the particular hardness was produced in the body, these testsconclusively demonstrated that for all of the bodies, treated anduntreated alike, the natural frequency was the same and that, ascompared to the untreated body, the frequency of the natural beatvibration of the treated bodies had changed. Where the treated bodieshad experienced an increase in hardness relative to the untreated body,the natural beat frequency had increased, while where the hardness ofthe treated bodies was relatively less, the natural beat frequency haddecreased. Numerous runs of such tests with metal bodies, other thanthose of a single substantially chemically pure metal, confirmed theconclusion that the natural beat frequency, and thence the frequency ofthe second characteristic sinusoidal oscillation, is in fixed relationto the hardness of the bodies, varying in the same sense as thevariations in hardness. But, as shown by handbooks on materials, sincesuch other physical properties as grain size, tensile strength,elongation and ductility, vary in fixed relation with hardness, for allpractical purposes reliable deductions are possible as to the relationof the natural beat frequency and such other physical properties.

To determine whether the natural beat vibration frequencies wereconstant for a given hardness irrespective of the material of thebodies, my test bodies were all of the same configuration and dimensionsbut either of different proportions of the same materials or of the sameor other proportions of different materials. It was found that forcorresponding values of hardness, the frequencies of the natural beatvibrations were not constant for all materials and proportions ofconstituents but were different for different body compositions, whetherthe difference in composition was qualitative or quantitative. Since thenatural frequency of a body is a function of its composition, and henceof its modulus of elasticity and density, and in part of its geometricconfiguration, the conclusion follows that the frequency of the naturalbeat vibration is a function of the natural frequency and of the degreeof hardness.

It follows that it is possible to produce in a body which, judged by itsconstituents qualitatively and quantitatively, is capable of havingvalues of its physical properties different from the values theypresently have, any of the differing and desired values, by impressingon the body the particular natural beat vibration of the frequencycharacteristic of the particular desired value of the physical property.At the same time the body should be in such condition that the effectproduced by the natural beat vibration shall be retained indefinitely bythe body after it is removed from the influence thereof, such as is thecase on quenching heated bodies in the prior known methods for hardeningmetals, for example steel. In accordance with established internationalterminology, the term steel means any iron capable without furthertreatment of being forged. The possibility of hardening steel dependsprimarily on its carbon content. It will be recalled that in the usualmethods of hardening steel, the steel is cooled from a certaintemperature, as given by its phase diagram, lying above the criticaltemperature of the particular steel, the cooling being more or lessrapid thereby Withdrawing energy from the steel. Each such certaintemperature corresponds chemically to a certain state of solution, thatis, position of the carbon in the atom lattice. Considered physically,at such certain temperature the atom lattices and their components arein a given state of vibration, such state of vibration beingcharacteristic for that particular certain temperature. If now suddenlya sufficient amount of heat, that is, energy, is withdrawn from thesteel to cause its temperature to fall to about or below the criticaltemperature, such characteristic state of vibration is fixed andretained by the steel even on, and after, cooling to room temperature.

I have indeed found that by heating metals and metal alloys totemperatures above the phase conversion temperature, or while such bodesare still in their molten state during their production, the physicalproperties can be controlled as to magnitudes by impressing thereon thenatural beat vibration characteristic of the given hardness of theparticular body, the impressed natural beat vibration consisting of thenatural frequency and the second characteristic frequency as abovementioned. What the particular natural beat frequency to be impressedshould be is readily taken from a system of graphs previously obtainedin the manner substantially as below described. What the minimumtemperature of the particular body should be at which the natural beatvibration treatment should be initiated is readily determinable from thephase diagram of the system of the constituents composing the body to betreated, and is the temperature at which the phase of the actualproportions of the constituents of the body are convertible from thephase stable at normal temperature to the next adjacent phase stable attemperatures above normal. The application of the natural beat frequencyis continued until the body has cooled to substantially the martensitetransformation temperature, which in the case of carbon steels is about250 C. On subsequent examination the completely cooled body is found tohave the desired physical properties of which the applied natural beatfrequency is characteristic.

As has been stated, the instant method may be used on the bodies whilethey are in the molten state, the original melt being cast in its finalform, the dimensions being little altered by the instant method and thestresses and strains of quenching, or from any other source, beingsubstantially totally absent since the body always cools off at itsordinary rate as determined by its surrounding atmosphere without anysudden interruption. Thus most machining operations, such as lathe work,grinding, milling, etc., are either eliminated or substantially reduced.The use of the instant invention, which of itself requires no extensivecapital investment for the practice of the method, also results inappreciable savings by requiring Where the materials of the bodies arecommon carbon.

steels Without alloying constituents, it has surprisingly developed thatby treatment of the bodies by the instant method the pl'tfXS propertiesvalues which heucfore have be. alloy steels and have not, or only withgreat difficulty, been attainable with the prior known methods. Hencethe instant invention has the added advantage of substantiallyeliminating the use of those alloying ingredients which hitherto havebeen required to improve hardness, for example, to the required degreeand beyond the limits of the values obtainable, without such addedalloying constituents.

The foregoing, as well as the stated and other objects of the instantinvention, will be clearly understood from the following description ofmy invention and of illustrative embodiments of apparatus to practicethe method of my invention when read in connection with the heretoannexed drawing in which:

Figures 1A and 1B show schematically oscillograms of the vibratoryconditions in both the testing of the materials and the treatment of thebodies to determine, respectively to produce therein, definitemagnitudes in the values of their physical properties;

Figure 2 shows graphs depicting the relationship between an illustrativephysical property, the hardness in kilograms per square millimeter asabscissas and the natural beat vibrations in cycles per second asordinates of three bodies each of carbon steel of differing carboncontent;

Figure 3 shows a series of graphs of the same type as shown in Figure 2for alloyed steels of different compositions;

Figure 4 shows an illustrative apparatus for practising the method ofthe instant invention in which the energy of the natural beat vibrationcorresponding to the desired value of a physical property is inductivelyimpressed on the body under treatment; and

casting under treatment.

Referring to the drawing, Figures 1A and 1B are diagrams to assist inthe understanding of the concept of beat vibrations in the physicalsense. To obtain the necessary knowledge of the interrelation betweenthe physical properties of bodies of materials, the materials not beingchemically pure as above stated, and the natural beat vibrationsrequisite to the instant invention, an oscillographic record is made ofthe vibrations of uniformly shaped and dimensioned test pieces of theparticular material. in making such records I have used cylindrical testpieces of standard dimensions, namely of 200 mm. in length and 20 mm. indiameter. Irrespective of which material, or the ratio of itsconstituents, it was found that the maximum natural frequency involvedwas of the order of some 2790 cycles per second, i. e., within the audiorange. For a given material an unhardened test piece, that is, one whichhas not been subjected to any special hardening treatment, was firsttested. The testing took the form of supporting the test piece so thatit could freely vibrate on excitation, for example, by positioning thetest piece across a pair of spaced knife edges or by suspending itadjacent its ends by a pair of spaced loops, and then causing it tovibrate, for example by mechanically striking it with a hammer actuatedby a spring mechanism, or a relay controlled electromagnet, atappropriately spaced time intervals. The test piece would then vibrate,with damping, at its natural frequency and, as has been repeatedlystated provided the test piece was not of a chemically pure singleelement, the second characteristic sinusoidal oscillation woulddemonstrate its presence in the form of the resultant natural heatvibration. A microphone positioned near the vibrating test piece, picksup the mechanical vibrations and, preferably through the intermediary ofan amplifier, transmits the vibrations electrically to a looposcillograph. Quite obviously in the place of the microphone anelectrical sound recorder may be used as the electroacoustic transducerprovided precautions are taken to shield the sound recorder from anydirect influence by the actuation sources for vibrating the test pieces.

When the photosensitive recording strip, which may be film or paper, ofthe oscillograph recorder is run at very slow speeds the envelope curve1 of Figure 1A, that is, the natural beat vibration which is theresultant of the natural frequency oscillation and the secondcharacteristic sinusoidal oscillation above identified, is recorded. Theinternodal interval T of one complete beat vibrati n, as is known, isequal to the reciprocal of the natural beat frequency which is thusaccurately determinable; since the frequency of a beat vibration isequal to the difierence of the two sinusoidal frequencies, which make upthe beat vibration. Obviously and as is well known, the magnitude of Tcan be determined by time marks on the oscillogram or by simultaneouslyrecording a known standard undamped frequency thereon.

When, however, the photosensitive recording strip is run at very highspeeds through the recorder, the individual oscillations 2, shown Withinthe envelope curve of Figure 1A, and of which one is shown in Figure 1B,are recorded,- the successive amplitudes of the oscillations 2varying'in accordance with the beat vibration 1 and having a frequencywhich is the arithmetic mean of the natural frequency and the secondcharacteristic frequency for the particular value of the physicalproperty. The record so produced, shown in Figure 1B, is acorrespondingly enlarged record for the time interval At of Figure 1A.Again the value of an internodal interval Azof the record of Figure 1Bis determinable in the well known manner above mentioned for determiningthe value T Having determined At and its corresponding frequency, andhaving previously determined the natural beat frequency i the values ofboth the natural frequency and the second characteristic frequency arereadily ascertainable mathematically.

When a test piece is of magnetic material, the excitation to cause it tovibrate 'may be by magnetostriction by placing a solenoid about the testpiece, the coil being energized from a variable, low frequency source.With such arrangement, the test piece is set into mechanical vibrationby the alternating field of the solenoid, the frequency of the sourcebeing varied until the amplitude f the vibration of the test piece is amaximum. At this latter point the test piece will be vibrating at itsnatural frequency. With this type of an arrangement, an electroacoustictransducer not subjectible to the direct influence of the solenoidfield, for example a crystal microphone, is preferably employed torecord the mechanical vibration of the test piece.

Having completed the above described observations, measurements andcomputations with the untreated test piece of a given material andcomposition, additional test pieces of the same material, composition,and dimensions but which have been treated in respect of their physicalproperties, for example of different degrees of hardness, are similarlyexamined. The particular sequence of examining the untreated and treatedtest pieces does of course not matter. From a comparison of the resultsobtained, it is readily apparent that while the natural frequency of thetest pieces of a given composition of materials is unaltered, assumingmeasurement thereof at identical temperatures, no matter what theparticular value of the physical property, for example hardness, thefrequency of the natural beat vibration changes in direct relation tothe increase in the value of the physical property On plotting in agraph the observed values of the natural beat frequencies against thevalues of the particular physical property, in the illustrative examplehardness, a fixed relationship between the two is readily noted. Inother words, the natural beat vibration is a measure of the value of thephysical property, hardness, of thematerial under test. Illustrativegraphs so obtained are shown in Figures 2 and 3 in which the naturalbeat frequencies are plotted against the corresponding hardness values.

Figure 2 shows such graphs, the natural beat vibrations in cycles persecond and the corresponding hardness values in kilograms per squaremillimeter, for three carbon steels which are typical of the regions inwhich they are positioned in the phase diagram of the iron-carbonsystem. Graph I is for a carbon steel in the hypo-eutectoid region,graph II for eutectoid carbon steel, and graph III for a carbon steel inthe hyper-eutectoid range. The hypereutectoid steel, having sulphur andphosporous constituents each of which is not in excess of 0.06% withboth together not exceeding 0.10%, had a carbon content of some 0.45%byweight. It will be noted that in the un treated condition, thehardness of the steel was 190 kg./sq. 111111., and a natural beatfrequency of 4 cycles per second. The natural frequency of the testpiece of this material was approximately 1950 cycles per second andremained unchanged in respectto all test pieces of this hypoeutectoidsteel, while the natural beat frequency 8 progressively increases withincreasing hardness to 16 cycles per second for the highest valueofhardness obtained with test pieces of the stated configuration anddimensions, 275 kg./sq. mm. The eutectoid steel for which graph 11shows'the interrelation had a carbon content of-"0.90% by weight and anatural frequency of some 2000 cycles per second which remained constantfor all values of the hardness, while'its natural beat vibrationfrequency increased from 4 cycles per second for a hardn. or 205 lug/sq.'mm., in its untreated condition to 16 cycles per second for the maximumhardness measured, 295 leg/mm? Similarly the natural frequency of 2090cycles per second of the test piece of hypereutectoid steel of a carboncontent of 1.3% remained constant, from a hardness of 220 kg./Inm. inthe untreated condition'and a natural beat frequency of 3 cycles persecond, to the maximum hardness measured of 308 kg./mm.3 with a naturalbeat frequency of 20 cycles per second. Graphs IV to IX inclusive ofFigure 3 are similar to those of Figure 2, and similarly arrived at, forcertain alloy steels. used more or less extensively in industry. Theysimilarly show a fixed relation between the natural beat frequencies ofalloy steels to their corresponding hardness values. The alloy steelsfor which such graphs are given in Figure 3 had the followingcompositions in percentages by weight with the balance in each caseiron:

Graph 0 F Si Mn P S Or Mo Ni V 0. 40 0. 35 0.75 0. 020 0. 022 0. 440.18 1. 72 0. 024 0. 021 0. 44 0.30 0. 45 O. 026 0.022 0. 42 O. 35 0. 930. 020 O. 020 0. 43 0. 21 0. 65 0. 026 (J. 024 0. 59 0. 29 0. 60 0. 022O. 023

The graphs of Figures 2 and 3 are illustrative only, since I have infact prepared, as the result of examinations as above described, graphsfor steels of numerous other compositions used in industry and thepractical arts, all of which examinations and their graph-plottedresults show the interrelation between the natural beat vibrationfrequency and the hardness corresponding thereto. V

Not only do steels show such interrelation between the physical propertyvalues and the natural beat vibration frequency but also bodies made ofmetals and metal alloys of which the major ingredient is other thaniron. All metal alloys having a phase diagram of the system of theircomponents, which have at least two stable conditions of their combinedconstituents in exactly the same basic Way show the interrelation of thephysical property values of bodies made thereof and their natural beatvibration frequencies as above enumerated and described for steel andsteel alloys. The alloys set forth in the textbook by Dr. M. Hansenentitled Der Aufbaui der Zweistofliegierungen, published by Verlag vonJulius Springer, Berlin 1936, are herewith incorporated by reference asthough actually here enumerated in detail.

The graphs shown in Figures 2 and 3 are all, plotted with the naturalbeat frequencies as the ordinate and the hardness as the abscissa. It isof course to be understood that the graphs may have some other physicalproperty; such as strength, ductility, or grain size, etc., as theabscissa in view of the known close interrelations therebetween and thehardness of a given material andbody. I have used as the abscissa ineach of Figures 2 and3 the various values of hardness as they are mostreadily directly measurable with available equipment, but. expressly donot limit myself to the graphs being in exactly this form. r H

Assume now that it is required that a given value, other than that whichis presently possessed by a body. of known materials and lrnown'ratio ofconstituents, bejbrought about in a given physical property of the body,Since the illustrative graphs of Figures 2 and 3 are in respect seasonsof hardness, we will assume the desired value is in the hardness. Forthe time being, we will further assume that the body to be treated -3 ofboth the materials and the ratio thereof for which we have previouslymade a graph and that it is also of the same configuration anddimensions as the test pieces for which the graph was made. The requiredhardness is located on the graph and the natural beat vibrationcorresponding thereto is read therefrom. For example, assume that anuntreated body of the hypoeutectoid steel of graph 1 which is of thesame dimensions as the test pieces in making graph 1 is to be given themaximum hardness of 275 kg./mm. which is shown by point A of graph 1,and discloses that the natural beat frequency is 16 cycles per second.The body is now placed in a furnace and heated to above the phaseconversion temperature for 0.45% C. carbon steel, which is some 780 C.from the phase diagram for FezC systems. Upon reaching this temperaturethe body is removed from the furnace and subjected for a period of fromfour to ten minutes to the natural beat vibration frequency of about 0.5kilowatt power and formed by two sinusoidal oscillations of 1950 cyclesper second and 1966 cycles per second the irradiation of the body by thenatural beat frequency being stopped when the body has cooled to about250 C. Examination thereafter of the treated body at normal temperaturediscloses that the hardness of the body has increased from its value inthe untreated body by some 22.3%, from 190 l;g./mm. to 275 kg./mm. Whentesting the body now by the procedure her in before described forproducing the graphs, its natural beat vibration frequency will be foundto be 16 cycles per second as compared to one of 4 cycles per second inthe untreated condition.

Not always is the body of a given material for which a graph has beenmade of the configuration and dimensions of the test pieces by which theavailable graphs have been made. in such case the natural frequency ofthe particular body to be treated may either be mathematically computedfrom the graph available, that is, from the additional data giventhereon as to size, configuration, and natural frequency of the bodiesfor which the graph Was made if the bodies used to make the graph areother than the normalized test pieces, or in the alternative may beexperimentally determined. Thus assuming that a body made of thehypoeutectoid steel of graph I and having a natural frequency of 3000cycles per second is to be treated so that its hardness is 275 kg./mm.In this instance the natural beat vibration frequency used for thetreatment of the body would be composed of the two sinusoidaloscillations of 3000 cycles per second and of 3016 cycles per second togive a frequency of 16 cycles per second for the corresponding naturalbeat vibration as shown by the ordinate of point A of graph 1.

So also, an untreated body of a given material may not always be desiredto be treated to impart to it the maximum possible hardness; thus thehardness value of 232 leg/mm? may be desired for a body of the steel ofgraph i. Point B of graph 1 shows the natural beat vibration to be 12cycles per second. Assuming the body to be treated has a naturalfrequency of 3000 cycles per second, the other sinusoidal oscillationmaking up the natural beat vibration is therefore 3012 cycles per secondin frequency.

Then again it may not always be desirable or desired to increase thevalue of the physical property from the value the property presentlyhas. That is, for one spe cific purpose or other it may become desirableto decrease the value of the hardness of bodies which may previouslyhave been treated. Again the graph for the particular material isconsulted and the beat frequency natural to the desired degree is noted.The procedure is now as above stated in respect of heating to above thephase conversion temperature and irradiating the body with the propernatural beat frequency vibration corresponding to the desired decreasedvalue of the hardness while the. body 10 is cooling from above its phaseconversion temperature to well below such temperature. As before, whenthe treated body has cooled to normal temperature, it has the desiredand decreased value of hardness and exhibits the corresponding naturalbeat vibration frequency.

In the illustrative apparatus for practising the method of the instantinvention, shown in Figure 4, a body 10 of magnetic material, afterhaving been heated to a temperature of some 800 C. to 1,000 O, isinserted in supported on a pair of spaced supports of fire rematerial12. The coil 11 is connected in the output circuit of the poweramplifier 13 of which the input is supplied with energy from a pair oflot -frequency generators, Ma and 14b, through the transformers Theoutput of each oscillation generator is varia in frequency, bothgenerators being preferably provided with separator stages to eliminatehysteresis coupling effects when they are mutually detuned. One of thegenerators, 140 or 145, is tuned to the frequency equal to that of thenatural frequency of the body, which frequency is known in the case ofmass production or is measured in the manufacture of single pieces. Bythe use of the graphs as above illustrated, the natural beat frequencyis noted for the desired value of the physical property, and the otherof the generators, 24!) or ida, is tuned to the frequency higher thanthat to which the first generator is tuned by the value of thecorresponding natural beat frequency. Thus as the body 10 cools fromabove the phase conversion temperature it is sympatheticallymeclianically vibrated in synchronism with the impressed magneticvibrations so that the corresponding vibratory condi ion of the atomlattice of the body is fixed and held v/ 11!: and as the temperature or"body falls to below the phase conversion temperature toward .d about themartensite transformation temperature.

The specific means and apparatus used to vibrate the body undertreatment by the n .iod of the instant invention the desired naturalheat vibration frequency may be varied in many details, some of whichmay depend on the nature of the particular material being l or" theknown means of the electroacoustic elation t may be so employed inprinciple, for ex- 45 ample, ma etostrictive, electrostrictive,electromagnetic,

or elec means, etc., and particularly in the oduction items by themethod of ieh items have low natural he beat vibrations may be producedby 1 .mati form shows a form 0. apparatus which may used, by way orillustration, in the very practical application of the method of theinstant inven- Jon its being cast and The two member, 11 the usualpouring mold base men? l :d by the metal eleshown and .irough -ectrodesare con- .ry a trans Amer 21, the secondmade a conductor of rgecross-section and is connected to the output of a a pair of low-freworeconnected in parallel in the the low electrical resistance of from itsmolten state nts, for example of torough the casting and By immediatelyso passing currer. through the casting while it is solidifying, and withappropriate selection of the natural beat vibration In a a with the de dvalue of the Ill physical property, the-desired value'o'f the physicalprop erty is obtained in the solidified casting. By the use of themethod of the instant invention in this manner it is possible to impartto castings while still in the molten state and solidifying, propertieswhich heretofore could only be imparted to them by appropriate treatmentsubsequent to their solidification. It is surmised that in thisparticular practice of the method of the instant invention, the electricoscillations are translated electrodyn-amically into mechanicalvibrations.

The method of the instant invention is readily applicable in themanufacture of steel by making use of existing apparatus in the steelplants. In such practical applications, a flow of gas may be directedabout the material to be treated, and at least one of the sinusoidaloscillations making up the natural beat vibration is impressed on theflow of gas, which in turn transmits such oscillation, or oscillationsas the case may be, to the material to be treated. While both sinusoidaloscillations constituting the natural beat vibration of the desiredvalue of the physical property are preferably impressed on the stream ofgas, if but one is so impressed on the gas stream then the othersinusoidal oscillation thereof is impressed directly on the materialbeing treated. Whereas with prior irradiation methods using supersonicfrequencies to improve bodies while in their solid or molten condition,matching difliculties impair the transfer of sufficient energy from agaseous space into a solid or molten body, such difliculties are largelyeliminated when using the method of the instant invention in that,firstly, the two sinusoidal oscillations comprising the natural beatfrequencies lie in the resonant range of the body under treatment sothat relatively little excitation energy is required to release powerfulforces; and secondly, the oscillations corresponding to the naturalfrequency of the particular body are relatively low so that absorptionof oscillatory energy by the treated material is much less than in theprior supersonic methods; hence in the instant method, in thisapplication as in all its applications, the depth of penetration of theexcitation oscillations into the body under treatment is correspondinglygreater and extends to all portions of the body whether surface orinternal regions. Due to the resonant effects which so appear, theentire body is uniformly affected in the instant method. The blowerequipment presently installed in any steel plant irrespective of theprocess pr-cticed for producing steel, may readily be used as theapparatus for practicing the instant invention. Thus, for example, thegas stream may be passed through fixed oscillation generators which aretuned or tunable,

the exciting energy being taken directly from the gas stream. On theother hand, sirens with motor drives, or electroacoustic transducers ofany of the known types, may be used to impress the undamped oscillation,or oscillations, of the natural beat vibration on the gas stream. Whereboth oscillations of the natural beat vibration are impressed on the gasstream, two tuned or tunable generators may be disposed in series, butare preferably disposed in parallel branches of the gas stream.

While my own work in the conception and development of the instantmethod has been with relatively crude apparatus and facilities, I stressthat the method of my invention always results in reproducible effectsand values.

. Further, as has hereinabove been stated, the instant method whenapplied to the treatment of castings in their molten state substantiallyavoids all stresses and strains in the cast body. It is known thatcertain alloy steels, for example stainless steel alloys, in spite oftheir advantages otherwise, are used rather sparingly industriallybecause of their tendency to crystallize so coarsely on cooling afterbeing cast that they simply cannot be cold worked thereafter. As is wellknown, the size of the crystals depends on the composition of the steeland the cooling rate; in general, the slower the cooling the larger thecrystals will be. If the solidification is slow, crystallizationproceeds from the casting exterior walls inwardly toward the center andforms macroscopic tree-like bodies of austenite, or dendrites. Sincecrystallization involves grain growth, the instant method isparticularly advantageous in eliminating deleterious cracks in thecasting which presently cause an appreciable percentage of such steelalloy castings to be rejected for further industrial use. By applying tothe ingot or casting in the mold in the molten condition the naturalbeat frequency corresponding to the required degree of grain finenessfor the particular alloy steels, the crystal size will be such that thedevelopment of cracks is avoided and hence these alloy steels take onrenewed and increased industrial value and importance. Furthermore, inprior endeavors to treat castings in the molten condition while themolds, the relationship of the superficial surface of the casting to itstotal volume had to be relatively large in order to obtain the requireddegree of grain fineness, and to avoid cracking and shape distortions inview of the feasible cooling rates in such prior methods. With the useof the instant method the relationship therebetween, that is the ratioof external surface to volume of the casting, is absolutely immaterialand may be of any order. Irrespective of the volume or the surface, thephysical properties of castings may, by the instant method, be given anydesired values within the possible range as determined by theconstituents of the castings, and be given such values throughout thecasting.

Since the natural beat frequency depends on the elastic anisotropy ofbodies, it follows, of course, that not only are electrically conductivebodies treatable by the instant method but also bodies of dielectricmaterials. As is known, the appearance of absorption lines in thespectra of bodies is computable from the elastic constants of themolecules, the observed values agreeing closely with the computedvalues. But the absorption spectra of metals and metal alloys differfrom those of all non-metallic bodies only in that the absorption bandsof the former are continuous while those of the latter arediscontinuous, the continuity of the bands in the metals and metalalloys (electrical conductors) being caused by the free electrons whichproduce the electrical conduction, while in the non-metal bodies(electrical non-conductors) there are no free electrons and hence thereis an absorptionless gapin the spectra thereof. Furthermore in anelectric field every body becomes a dipole, conductors by induction andinsulators by electrical charging of the dielectric. When the electricalcharging and reversal of charge is by means of an alternating electricalfield vibrating in synchronism with the natural frequency and thenatural beat frequency-the natural beat frequency corresponding to thedesired value of the physical property--the values of the physicalproperties of a dielectric material are readily controllable, asisreadily understandable, just as are those of a conductive body by theinstant method.

All the apparatus, arrangements and interconnections of the apparatusshown, or suggested, are by way of illustration only and are in no wayto be considered as limitations. Various modifications thereof andtherein will suggest themselves to the skilled worker in the art withoutdeparting from the scope and spirit of my instant invention.

What I claim is:

1. The method of producing any desired value within range of possiblevalues of a physical property of a body' consisting of at least twocomponents, comprising the steps of heating the body to at least itslowermost phase conversion temperature, subjecting the heated body tothe influence of beat oscillations of a frequency characteristic of thevalue of the physical property, the beat oscillations being theresultant of an oscillation frequency equal to the natural frequency ofthe body and a second oscillation of a frequency equal to the sum of thenatural frequency of the body and the natural beat frequency.

assays characteristic of the value of the physical property, andmaintaining the body subject to the influence of the beat oscillationswhile the body cools to a temperature substantially below such phaseconversion temperature.

2. The method of producing any desired value Within a range of possiblevalues in the hardness of a body consisting of at least two components,comprising the steps of heating the body to above its lowermost phaseconversion temperature as determined by its components, subjecting theheated body to the influence of the natural beat frequency vibrationcorresponding to the value of the hardness, and maintaining the bodysubject to the influence of the natural beat vibration until the bodyhas cooled to a temperature substantially below such phase conversiontemperature.

3. The method of controlling the values of the physical properties ofbodies of material consisting of one major ingredient and at least oneminor ingredient, comprising the steps of heating the body to at leastits lowermost phase conversion temperature as determined qualitativelyand quantitatively by its ingredients, subjecting the heated body tobeat vibration oscillations of a frequency equal to the natural beatfrequency corresponding to the value of the physical properties, andpermitting the body to cool while maintaining the body subject to thebeat vibration oscillations.

4. The methods of controlling the values of physical properties of ametal body consisting of a major ingredient and at least one minoringredient, comprising the steps of heating the metal body to atemperature above its lowermost phase conversion temperature, subjectingthe so heated metal body to the influence of externally produced beatoscillations of a frequency equal to the frequency of the natural beatvibration corresponding to the value to be imparted to the physicalproperties, and. permitting the metal body to cool at the ratedetermined by the ambient atmosphere to substantially below such phaseconversion temperature while maintaining the body subjected to theinfluence of the beat oscillations.

5. The method of producing any one of a number of values possible in aphysical property of a body of material having at least two components,comprising the steps of heating the material to its molten condition,forming the body of the molten material, subjecting the formed bodywhile still in the molten condition to the influence of beat frequencyoscillations of a frequency equal to that of the natural beatoscillation of the body corresponding to the value to be imparted to thephysical property, and maintaining the body subject to the influence ofthe beat oscillations while the formed body solidifies.

6. The method according to claim 5 in which the beat frequencyoscillations are electrically produced and applied conductively to theformed body.

7. The method of producing any desired value within the range ofpossible values in the hardness of a body consisting of at least twocomponents, comprising the steps of heating the material to its moltencondition, forming a body of the molten material, subjecting the formedbody while in the molten condition to the influence of a beat frequencyoscillation of the frequency equal to that of the natural beat vibrationof the body corresponding to the value to be imparted to the hardness,and maintaining the body subject to the influence of the beatoscillation until the body has solidified and cooled.

8. The method of producing any one of a plurality of possible values inthe physical properties of a body of material consisting of at least twoingredients, comprising the steps of forming a body of the materialwhile in its heated molten condition, directing a flow of gaseous mediumabout the body in its molten condition, impressing upon the flow of gasbeat oscillations of a frequency equal to that of the natural beatvibration of the formed body corresponding to the value to be impartedto the physical properties, the flow of gas impressing the beatoscillations in turn on the formed body of the molten material, andmaintaining the application of the beat oscillations while the bodycools and solidifies.

9. The method of producing any desired value within the range ofpossible values in the hardness of a body of metal consisting of atleast two ingredients, comprising the steps of forming a body of thematerial while in a heated molten condition, directing a flow of gasabout the formed body, impressing upon the flow of gas at least one of apair of sustained oscillations forming a beat frequency oscillation ofwhich the frequency is equal to that of the natural beat vibrationcorresponding to the degree of hardness to be imparted thereto, andmaintaining the gas flow and the impressed oscillation while the metalbody cools to at least complete solidification.

1G. The method of producing any desired value within the range ofpossible values which a physical property of carbon steels may have asthe result of its composition, comprising the steps of heating thecarbon steel body to above its lowermost phase conversion temperature asdetermined qualitatively and quantitatively by its carbon content,subjecting the steel body to the influence of beat frequencyoscillations of the frequency equal to the natural beat frequencycoresponding to the value to be imparted to the physical properties, andmaintaining the steel body under the influence of the beat frequencyoscillations as it cools to substantially the martensite transformation.

11. The method of producing any desired value of hardness within therange of possible values of the hardness of carbon steels, comprisingthesteps of heating a body of carbon steel to at least the lower of itsphase conversion temperatures of the particular carbon steel, subjectingthe steel body in the heated condition to the influence of beatoscillations of which the frequency is equal to that of the natural beatvibration of the particular carbon steel corresponding to the value tobe imparted to the hardness, and maintaining the steel body subject tothe influence of the beat frequency oscillations as it cools to belowabout 400 C.

12. The method according to claim 11 in which the carbon steel body isheated to a temperature lying in the range from such lower phaseconversion temperature to about 1000 C., the steel body is subjected tothe influence of the beat oscillations for a period of from four to tenminutes, and the body is permitted to cool at the rate determined by theambient temperature.

13. The method according to claim 11 in which the beat oscillations areelectrically generated and conductively applied to the steel body.

14. The method according to claim 11 in which the beat oscillations areelectrically generated and inductively applied to the steel body.

15. The method of producing any desired value within the range ofpossible values in the hardness of a carbon steel body, comprising thesteps of casting a steel body, subjecting the steel casting while stillin its molten condtion to the influence of electrically produced beatfrequency oscillations of a frequency equal to that of the natural beatvibration of the casting at normal temperatures corresponding to thevalue to be imparted to the hardness, and maintaining the castingsubject to the influence of the beat oscillations until the casting hassolidified and cooled to substantially the temperature of the martensiteregion.

16. The method according to claim 15 in which the beat oscillations areapplied to the casting by electrical conduction, and the casting ispermitted to cool at the rate determined by the ambient atmosphere.

References :Cited in the file of this patent UNITED STATES PATENTS1,061,760 Lash May 13, 1913 {@tlaer references on following page)

